1. Field
The invention relates generally to asphalt emulsifiers, asphalt emulsions and methods to produce the emulsifiers.
2. Description of the Related Art
In the manufacture of pale wood rosin from southern pine stumpwood, crude rosin is extracted from the wood and then refined using solvent/solvent partitioning between aliphatic hydrocarbon and polar solvents. One of the by-products of this operation is a dark, high melting, largely aliphatic hydrocarbon-insoluble resin, hereinafter referred to as AHI resin. AHI resin is a thermoplastic resin that chemically is a complex mixture of high molecular weight phenolic compounds, rosin acids, neutral materials and several minor components. An AHI resin is produced as described in U.S. Pat. No. 2,221,540, which patent is incorporated herein by reference in its entirety. A preferred AHI resin is Vinsol® resin available from Pinova, Inc., Brunswick, Ga.
AHI resin, particularly Vinsol® resin from Pinova, Inc., Brunswick, Ga., is used in a wide variety of industrial applications including asphalt emulsions. Asphalt emulsions are used in a variety of applications such as road building, road sealing, soil stabilization, mulching, surface coating of asphalt pavements, and built-up roofs. The amount of wood rosin available by solvent partitioning is limited by the process equipment, and by environmental and cost constraints. Because the amount of wood rosin produced is limited, the supply of AHI resin available for industrial applications is also limited. Consequently, there is a need for a material which will perform in asphalt emulsions in a manner similar to AHI resin. Furthermore, it is desirable for asphalt emulsifiers to be produced with processes as green as possible. Green processing involves “minimal to no” hazardous materials, and minimal waste.
U.S. Pat. No. 5,656,733 describes resinous compositions comprising lignin and polymerized rosin, and the use of such compositions as asphalt emulsifiers and air entraining agents for concrete. U.S. Pat. No. 6,512,090 describes asphalt emulsions that are produced from reactions of solutions of alkali metal hydroxides and ammonium hydroxide with solidified pyrolytic wood tar. In this process, pyrolytic wood tar oil is produced by the fast pyrolysis of pine wood followed by rapid quenching of the gas product vapors. The pyrolytic wood tar is then subjected to carefully controlled distillation and evaporation of the volatiles including water, which also produces cross linking of reactive sites on the lignin fragments.